U.S. patent number 7,043,653 [Application Number 10/215,228] was granted by the patent office on 2006-05-09 for method and apparatus for synchronous signal transmission between at least two logic or memory components.
This patent grant is currently assigned to Infineon Technologies AG. Invention is credited to Justus Kuhn, Hermann Ruckerbauer, Frank Thiele.
United States Patent |
7,043,653 |
Kuhn , et al. |
May 9, 2006 |
Method and apparatus for synchronous signal transmission between at
least two logic or memory components
Abstract
An internal clock signal of a logic/memory component that
receives signals is transmitted as a reference clock to a
transmitting logic/memory component. With the aid of the reference
clock, the transmission clock of the output unit of the
transmitting logic/memory component is generated, such that
transmitted signals arrive in a receiving unit of the receiving
component synchronously with the internal clock signal of that
component.
Inventors: |
Kuhn; Justus (Munchen,
DE), Ruckerbauer; Hermann (Moos, DE),
Thiele; Frank (Munchen, DE) |
Assignee: |
Infineon Technologies AG
(Munich, DE)
|
Family
ID: |
7694761 |
Appl.
No.: |
10/215,228 |
Filed: |
August 8, 2002 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20030033551 A1 |
Feb 13, 2003 |
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Foreign Application Priority Data
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Aug 8, 2001 [DE] |
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101 38 883 |
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Current U.S.
Class: |
713/401; 713/400;
713/503 |
Current CPC
Class: |
G06F
1/12 (20130101) |
Current International
Class: |
G06F
1/12 (20060101) |
Field of
Search: |
;713/400,401,500,503 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Browne; Lynne H.
Assistant Examiner: Yanchus, III; Paul
Attorney, Agent or Firm: Greenberg; Laurence A. Stemer;
Werner H. Locher; Ralph E.
Claims
We claim:
1. A method for synchronous signal transmission between a first
component that sends signals and a second component that receives
the signals, which comprises the steps of: furnishing an internal
clock signal of the second component as a reference clock to the
first component over at least one clock line; delaying the
reference clock, arriving over the clock line, with an aid of at
least one delay unit of the first component, in such a way as to
delay a starting time for each cycle of the transmission clock
relative to a starting time for each cycle of the reference clock
by one cycle time, minus twice a signal transit time of the
reference clock, over the clock line between the first component
and the second component; and generating, with an aid of the
reference clock received and delayed, a transmission clock for an
output unit of the first component in such a way that the signals
transmitted over a signal line between the first component and the
second component are output synchronously with the reference
clock.
2. The method according to claim 1, which comprises reading out
data, command, and address signals only unidirectionally from the
first component to the second component over the signal line.
3. The method according to claim 1, which comprises transmitting
additional signals from the second component to a third component
using a transmitter/receiver unit, synchronously with the internal
clock signal.
4. The method according to claim 3, which comprises receiving the
additional signals in the third component from the second component
using a further transmitter/receiver unit, synchronously with the
internal clock signal.
5. The method according to claim 1, which comprises generating the
internal clock signal of the second component using an external
clock signal.
6. The method according to claim 1, which comprises generating the
internal clock signal of the second component using an internal
clock.
7. The method according to claim 1, which comprises transmitting
the signals, being in a form of test data, from the first component
to the second component, synchronously with the internal clock
signal, the test data being used for evaluation purposes
synchronously with the internal clock signal for a signal
transmission in at least one of a forward direction and a reverse
direction between the second component and at least one third
component.
8. In a first component that sends signals and a second component
that receives the signals, an apparatus for synchronous signal
transmission between the first component and the second component,
the apparatus comprising: a clock receiver disposed in the first
component; an output unit connected to said clock receiver and
disposed in the first component; at least one clock line connected
to said clock receiver; a clock transmitter disposed in the second
component, connected to said clock line, and furnishing an internal
clock signal as a reference clock to said clock receiver in the
first component over said clock line; and a signal line connected
between the first component and the second component, said clock
receiver with an aid of the reference clock generates a
transmission clock for said output unit of the first component in
such a way that the signals transmitted over said signal line
between the first component and the second component being output
synchronously with the reference clock; said clock receiver in the
first component having a delay unit to delay the reference clock
arriving over said clock line from the second component in such a
way as to delay a starting time for each cycle of the transmission
clock relative to a starting time for each cycle of the reference
clock by one cycle time, minus twice a signal transit time of the
reference clock over said clock line between the first and second
components.
9. The apparatus according to claim 8, wherein the second component
is a chip set having an integrated processor unit.
10. The apparatus according to claim 8, wherein the first component
is a dynamic random access memory.
11. A circuit having synchronous signal transmissions, comprising:
a first component having a clock receiver and an output unit
connected to said clock receiver; at least one clock line connected
to said clock receiver; a second component having a clock
transmitter connected to said clock line and furnishing an internal
clock signal as a reference clock to said clock receiver in said
first component over said clock line; and a signal line connected
between said first component and said second component, said clock
receiver with an aid of the reference clock generates a
transmission clock for said output unit of said first component in
such a way that the signals transmitted over said signal line
between said first component and said second component being output
synchronously with the reference clock; said clock receiver in said
first component having a delay unit to delay the reference clock
arriving over said clock line from said second component in such a
way as to delay a starting time for each cycle of the transmission
clock relative to a starting time for each cycle of the reference
clock by one cycle time, minus twice a signal transit time of the
reference clock over said clock line between said first and second
components.
12. The apparatus according to claim 11, wherein said second
component is a chip set having an integrated processor unit.
13. The apparatus according to claim 11, wherein said first
component is a dynamic random access memory.
14. The apparatus according to claim 11, wherein: said first
component is selected from the group consisting of memory
components and logic components; and said second component is
selected from the group consisting of memory components and logic
components.
15. The method according to claim 1, which comprises: selecting the
first component from the group consisting of memory components and
logic components; and selecting the second component from the group
consisting of memory components and logic components.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a method and an apparatus for synchronous
signal transmission between at least one first logic/memory
component that transmits signals and at least one second
logic/memory component that receives the signals.
Particularly in microprocessor or memory technology, message
signals, such as data, addresses, commands, or other signals are
transmitted among a plurality of logic/memory components. The
logic/memory components usually cooperate in such a way that a
first logic/memory component receives message signals from another,
further logic/memory component in order to further process them and
optionally transmit them on to a further logic/memory component,
for instance for storage or for further signal processing, and/or
to receive additional signals from the latter.
A method for synchronous signal transmission between a first
logic/memory component that sends signals and a second logic/memory
component that receives the signals, is described in U.S. Pat. No.
5,828,871. In the method, an internal clock signal of the second
logic/memory component that receives signals is furnished as a
reference clock to the transmitting first logic/memory component
via at least one clock line. With the aid of the received reference
clock, a transmission clock of an output unit of the transmitting
first logic/memory component is generated in such a way that the
signals transmitted via a signal line between the transmitting
first logic/memory component and the receiving second logic/memory
component are output synchronously with the reference clock.
Published, Non-Prosecuted German Patent Application DE 198 30 571
A1, describes a logic/memory component with delay units.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method
and an apparatus for synchronous signal transmission between at
least two logic/memory components which overcome the
above-mentioned disadvantages of the prior art methods and devices
of this general type, in which arriving message signals that have
been sent from a first logic/memory component can be received and
read out by a receiving logic/memory component essentially
synchronously with its internal reception clock or its internal
receiving clock.
With the foregoing and other objects in view there is provided, in
accordance with the invention, a method for synchronous signal
transmission between a first logic/memory component that sends
signals and a second logic/memory component that receives the
signals. The method includes furnishing an internal clock signal of
the second logic/memory component as a reference clock. to the
first logic/memory component over at least one clock line, and
delaying the reference clock, arriving over the clock line, with an
aid of at least one delay unit of the first logic/memory component,
in such a way as to delay a starting time for each cycle of the
transmission clock relative to a starting time for each cycle of
the reference clock by one cycle time, minus twice a signal transit
time of the reference clock, over the clock line between the first
logic/memory component and the second logic/memory component. With
an aid of the reference clock received and delayed, a transmission
clock for an output unit of the first logic/memory component is
generated in such a way that the signals transmitted over a signal
line between the first logic/memory component and the second
logic/memory component are output synchronously with the reference
clock.
According to the invention, the internal clock signal of the
signal-receiving logic/memory component is furnished as the
reference clock to the transmitting logic/memory component via the
clock line. With the aid of the reference clock, the transmission
clock of the output unit of the transmitting component for signals
to be transmitted is generated, in such a way that the signals
transmitted over the signal line arrive synchronously with the
internal clock signal of the receiving logic/memory component, in
its receiver unit, where they are read out from it synchronously.
The reference clock of the receiving second logic/memory component,
arriving via the clock line, is delayed with the aid of the delay
unit of the transmitting first logic/memory component, in such a
way as to delay the starting time for each cycle of the
transmission clock compared to the starting time for each cycle of
the reference clock by one cycle time, minus twice the signal
transit time of the reference clock over the clock line between the
two logic/memory components.
In this way, simple and reliable synchronization between at least
two logic/memory components is assured. Because the
signal-receiving logic/memory component uses its internal clock
signal, which actually trips the reception of the signals to be
transmitted in its receiver unit, as a reference clock for the
transmitting logic/memory component, and with the aid of the
reference clock a corresponding transmission clock for the output
unit of the transmitting component for the signals to be
transmitted is generated, a high degree of synchronicity in the
readout of the arriving signals relative to the internal clock
signal of the receiving logic/memory component is achieved. The
result is a substantial increase in the accuracy with which message
signals, such as data, addresses, commands, or other signals can be
transmitted between the transmitting and receiving components. Thus
higher data rates in communications between the two components can
be achieved, compared to conventional synchronizing processes that
specify the transmission clock and the reception clock for the two
components communicating with one another by a separate, external
clock line for each one.
In accordance with an added mode of the invention, there is the
step of reading out data, command, and address signals only
unidirectionally from the first logic/memory component to the
second logic/memory component over the signal line.
In accordance with an additional mode of the invention, there is
the step of transmitting additional signals from the second
logic/memory component to a third logic/memory component using a
transmitter/receiver unit, synchronously with the internal clock
signal.
In accordance with another mode of the invention, there is the step
of receiving the additional signals in the third logic/memory
component from the second logic/memory component using a further
transmitter/receiver unit, synchronously with the internal clock
signal.
In accordance with a further mode of the invention, there is the
step of generating the internal clock signal of the second
logic/memory component using an external clock signal.
In accordance with a further added mode of the invention, there is
the step of generating the internal clock signal of the second
logic/memory component using an internal clock.
In accordance with a further additional mode of the invention,
there is the step of transmitting the signals, being in a form of
test data, from the first logic/memory component to the second
logic/memory component, synchronously with the internal clock
signal. The test data is used for evaluation purposes synchronously
with the internal clock signal for a signal transmission in a
forward direction and/or a reverse direction between the second
logic/memory component and at least one third logic/memory
component.
With the foregoing and other objects in view there is provided, in
accordance with the invention, in a first logic/memory component
that sends signals and a second logic/memory component that
receives the signals, an apparatus for synchronous signal
transmission between the first logic/memory component and the
second logic/memory component. The apparatus contains a clock
receiver disposed in the first logic/memory component, an output
unit connected to the clock receiver and disposed in the first
logic/memory component, and at least one clock line connected to
the clock receiver. A clock transmitter is disposed in the second
logic/memory component, is connected to the clock line, and
furnishes an internal clock signal as a reference clock to the
clock receiver in the first logic/memory component over the clock
line. A signal line is connected between the first logic/memory
component and the second logic memory component. The clock receiver
with an aid of the reference clock generates a transmission clock
for the output unit of the first logic/memory component in such a
way that the signals transmitted over the signal line between the
first logic/memory component and the second logic/memory component
are output synchronously with the reference clock. The clock
receiver in the first logic/memory component has a delay unit to
delay the reference clock arriving over the clock line from the
second logic/memory component in such a way as to delay a starting
time for each cycle of the transmission clock relative to a
starting time for each cycle of the reference clock by one cycle
time, minus twice a signal transit time of the reference clock over
the clock line between the first and second logic/memory
components.
In accordance with an added feature of the invention, the second
logic/memory component is a chip set having an integrated processor
unit.
In accordance with a concomitant feature of the invention, the
first logic/memory component is a dynamic random access memory.
Other features which are considered as characteristic for the
invention are set forth in the appended claims.
Although the invention is illustrated and described herein as
embodied in a method and an apparatus for synchronous signal
transmission between at least two logic/memory components, it is
nevertheless not intended to be limited to the details shown, since
various modifications and structural changes may be made therein
without departing from the spirit of the invention and within the
scope and range of equivalents of the claims.
The construction and method of operation of the invention, however,
together with additional objects and advantages thereof will be
best understood from the following description of specific
embodiments when read in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block circuit diagram of a synchronous signal
transmission among a plurality of logic/memory components with
clock signaling in accordance with a method according to the
invention; and
FIG. 2 is a timing diagram showing a chronological sequence of a
clock signal in a receiving component of the configuration
according to FIG. 1, and in relation to it the chronological
sequence of the internal clock signal of the receiving component,
which is returned there as a reference clock to a transmitting
component, and the transmission clock, generated from the reference
clock, for the transmitting component for synchronous transmission
of message signals to the receiving component.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In all the figures of the drawing, sub-features and integral parts
that correspond to one another bear the same reference symbol in
each case. Referring now to the figures of the drawing in detail
and first, particularly, to FIG. 1 thereof, there is shown how for
a logic/memory component, in particular an IC (integrated circuit),
such as IC2, a signal transmission from and/or to further
logic/memory components can be performed synchronously with an
internal clock signal. In the present exemplary embodiment, message
signals SI are transmitted by a first, transmitting logic/memory
component IC1 to a receiving logic/memory component IC2, for
further processing in the latter. Such message signals SI can for
instance be data, addresses, commands, or other signals. In
addition, the logic/memory component IC2 communicates with a third
logic/memory component IC3. Messages signals DQ are exchanged
bi-directionally between the logic/memory component IC2 and the
third logic/memory component IC3 over a data line DQL; that is, the
logic/memory component IC2 sends message signals to and/or receive
message signals from the third logic/memory component IC3. The
message signals DQ exchanged can in particular be data, addresses,
commands, and other signals that are usual in microprocessor or
memory technology.
In order now to enable synchronous execution, in terms of the
internal clock of the logic/memory component IC2, of both arriving
and outgoing message signals, the data transmission and data
processing are normally synchronized by an external clock signal.
In FIG. 1, one such external clock signal EXT is delivered via an
external clock line CLKIN, with the aid of a phase locked loop
(PLL) component group PLG, both to the logic/memory component IC2
and to the logic/memory component IC3, separately, each via its own
associated data line CLK2, CLK3. If data furnishing and/or data
processing that is largely synchronous with the external reference
clock EXT is desired in the first logic/memory component IC1 as
well, then the external reference clock EXT would be analogously
distributed to it via its own external clock line CLK1 with the aid
of the PLL component group PLG. The external clock line CLK1 is
represented by dot-dashed lines in FIG. 1. Accordingly, the PLL
component group PLG has the function of distributing the external
clock signal EXT to a plurality of parallel outputs OU1, OU2 and
OU3, with the clock lines CLK1, CLK2, CLK3 connected to them, so
that the same external clock pattern is furnished simultaneously in
each case.
The external reference clock EXT is preferably formed by the
periodic succession of square voltage pulses, which succeed one
another at equidistant time intervals, so that a regular, cyclical
high/low bit pattern is formed. The cyclical clock pattern is
additionally shown in FIG. 1 schematically for the external clock
line CLKIN before it fed into the PLL component member PLG.
In the exemplary embodiment, the logic/memory component IC1 is
preferably embodied as a memory chip set, optionally with an
integrated processor, that serves to perform the actual data
processing. In comparison, the logic/memory component IC3 forms a
memory unit in particular, such as a random access memory (RAM),
dynamic random access memory (DRAM), or a synchronous dynamic
random access memory (SDRAM) component, or SGRAM component.
Accordingly within the context of the invention, the logic/memory
component is understood to be a logic or arithmetic unit, such as a
microprocessor chip, and/or a memory unit, such as a DRAM.
From the memory unit IC3, data are to be read out, and/or data DQ
are to be read in from the logic component IC1. The readout and
reading in is supposed to be effected synchronously with the
external reference clock EXT. For a chronological adaptation of the
signal or data processing in the logic component IC2 and in the
reading and/or writing processes in the memory component IC3 with
respect to the external reference clock EXT, the latter is
delivered separately to the two components IC2, IC3 by the PLL
component group PLG via the associated clock lines CLK2, CLK3.
Effects on transit time caused by clock lines of different lengths,
various capacitive and inductive overcouplings, various load
switching among the clock lines and memory components, temperature
fluctuations, process fluctuations in the production of memory
and/or chips, jittering effects (that is, invariance of the
chronological location of the leading edge of the high/low pattern
of the external reference clock) resulting from the
clock-distributing PLL member, and other interference effects can
cause time lags between the reference clock patterns transmitted
separately to the components IC2, IC3. In other words, a
chronological divergence can occur between the external reference
clock patterns at the input of the components IC2, IC3 as a result
of the effects of interference. This would impair the desired
synchronous data processing in the two components IC2, IC3 and the
data transmission between the two components IC2, IC3 with
reference to the external reference clock EXT. For this reason,
each component IC2, IC3 on its input side has a so-called delayed
locked loop (DLL) component, which at least with respect to the
frequency or periodicity of the external clock pattern EXT largely
assures synchronicity. Preferably, such a DLL component unit
generates its own clock pattern, which also largely again matches,
in terms of its chronological location, the chronological location
of the external reference clock EXT.
In FIG. 1, the DLL component DLL2 is provided in the component IC2.
At its output, via an electrical line TL3, it outputs an internal
reference clock COU21, which is largely synchronous with the
external reference clock EXT in terms of frequency and/or
optionally phase as well. The internal reference clock COU21 is
then used as a pattern or primary clock for the data processing in
the component IC2 and for the data transmission and/or data
reception in the component IC2.
In addition or independently of this, the internal clock signal
COU21 of the second logic/memory component IC2 can optionally be
generated with the aid of an internal clock ICL, which is shown in
dot-dashed lines in FIG. 1 for the component IC2. Analogously, the
internal clock can optionally also be furnished for the memory
component IC3. The internal clock signals of the two components
IC2, IC3 are expediently adapted in terms of frequency and phase to
achieve the most synchronous possible clock specification.
The internal reference clock COU21 and the second logic/memory
component IC2 is thus formed, corresponding to the external clock
signal EXT, preferably by a periodic succession of square voltage
pulses that succeed on another at equidistant time intervals,
forming a regular, cyclical high/low bit pattern. One leading edge
each of the high/low pattern defines a starting time for the data
processing or further data transmission of the components IC2, IC3.
If only the leading edges of the square pulses of the reference
clock are used for defining starting times, then the term typically
used is single data rate operation. In comparison, twice the
operating speed in data processing can be achieved by providing
that the trailing edges of the square pulses of the reference clock
EXT are also used for defining starting times for data processing.
This mode is known in the memory or chip industry as the double
data rate processing mode.
In the component IC3 as well, a DLL delay unit DLL3 is
correspondingly provided on the input side, by which an internal
clock signal COU32 is furnished on the output side on a clock line
TL3. The internal clock signal COU32 is synchronized in terms of
its frequency with the external reference clock EXT and is made to
match the chronological location of the leading pulse edges
thereof. DLL units in practice, however, assure synchronicity of
the externally supplied reference clock patterns only to a certain
degree. Particularly, difficulties can arise in terms of the
synchronicity of the phase relationships of the leading and/or
trailing edges of the square pulse pattern of the particular
reference clock applied to the input side on the clock lines CLK2,
CLK3. This problem becomes all the more critical, the higher the
demanded frequencies for data processing are, since in that case
the decision times for allocating a higher low level become
shorter. This increases the risk of misallocations from transit
time delays. Accordingly, if even greater accuracy in terms of the
synchronicity of data processing in both components IC2, IC3 is
demanded, for instance because of high processing frequencies, then
expediently an additional indicator signal DQS (data query strobe)
is separately transmitted between the two components IC2, IC3. The
indicator signal DQS travels in the respective transmission
direction of the data signal to be transmitted and informs the
receiving component of the exact instant of reception for the data
signals DQ (data query) to be transmitted. For instance, if the
data signals DQ are to be transmitted over the data line DQL from
the memory component IC3 to the logic component IC2, then the data
signals DQ are output into the data line DQL in the component IC3
with the aid of a driver or output unit T3, which operates in
cadence with the internal reference clock COU32, in accordance with
the clock times of this clock pattern. In addition, via the
information line DQSL, the indicator signal DQS is transmitted,
again in accordance with the internal reference clock COU32, to the
logic component IC2, for the sake of unambiguously indicating to
the latter component the specific instant of reception for the
applicable data signal. The two transmission lines DQL, DQSL are
preferably embodied as largely matching in type, length, and
transmission properties. A precondition of this type of data
transmission by an indicator signal is that the applicable
transmitter component have a reference clock available, which is
expediently also furnished to the receiving component. The message
signals DQ transmitted from the memory component IC3 are received
in the logic component IC2 with the aid of a driver unit T23. The
driver unit T23 expediently has a receiver unit for this purpose.
For bi-directional signal transmission between the two components
IC2, IC3, the driver unit T23 expediently also implements a
transmission function, so that data can also be transmitted in the
opposite direction, from the logic component IC2 to the memory
component IC3, in a corresponding way with the aid of the indicator
signal DQS. The driver unit T23 is likewise clocked with the
internal reference clock COU21 in terms of the instants of
reception and transmission of the data signals DQ to be
transmitted.
The writing or in other words transmission of data signals DQ from
the second logic/memory component IC2 to the third
logic/memory-component IC3 is affected individually preferably as
now described.
The signals DQ, DQS are driven by the logic/memory component IC2.
The applicable indicator signal DQS there is center-aligned with a
respective associated data signal DQ to be transmitted, or in other
words, the leading edge of the applicable indicator signal DQS
comes approximately in the middle of the data window of the
applicable data signal DQ. Thus the particular indicator signal DQS
and the data signal DQ associated with it and to be transmitted are
phase-offset from one another by 90 degrees. The logic/memory
component IC3 takes over the respective arriving data signal DQ
having the leading and/or trailing edge of the indicator signal
DQS.
The reading of data signals DQ from the third logic/memory
component IC3 to the second logic/memory component IC2 is
preferably affected as now described.
The signals DQ, DQS are driven by the logic/memory component IC3.
Both outgoing signals have their leading edge at the same instant;
that is, there is no phase displacement but instead there is phase
synchronicity. If the applicable indicator signal DQS arrives at
the second logic/memory component IC2, it is phase-displaced there
by 90 degrees, and only then is the value of the arriving data
signal taken over. By the 90 degree phase offset performed in the
logic/memory component IC2 for the indicator signal DQS, in each
case the middle of the associated data window DQ, transmitted
simultaneously by the memory component IC3, is indicated, and the
readout of the data signal DQ is initiated.
A precondition of this type of data transmission is that the
applicable transmitter component make the reference clock
available. Moreover, a generation function in the applicable
transmitter component for the additional indicator signal, and an
evaluation function in the respective associated receiving
component for the indicator signal, are required. Under some
practical conditions this may be too complicated, or may not be
supported by the particular logic/memory component or even
implemented at all.
In order now, without this type of bi-directional transmission (by
use of an additional indicator signal DQS) to be able to transmit
message signals SI synchronously from at least one further, in this
case the first logic/memory component IC1 to the internal reference
clock COU21 of the receiving component IC2 over a data line TL12,
it is now possible in the simplest case also to send the external
reference clock signal EXT onward to the input of the component IC1
by the PLL member PLG over the external clock line CLK1 (shown in
dot-dashed lines). The external reference clock signal EXT would
then, in a manner corresponding to the other two components IC2,
IC3, also be corrected by a DLL unit DLL1 analogously in terms of
any possible type offset compared to the original, external
reference clock pattern EXT, and finally would be transmitted over
an internal clock line TL1 to a driver or transmitter unit AT1. The
externally supplied reference clock pattern would then define the
transmission instants for the message signals SI to be transmitted.
Nevertheless, if such an external reference clock signal EXT is
supplied separately and parallel to the various logic/memory
components, such as IC1, IC2, IC3 for the sake of their synchronous
data processing mode and/or for the data transmission, it could
happen that the reference clock signal in the various components or
chips involved in the data communication may look somewhat
different. Such effects can be caused for instance by interference
in the phase relationship, in particular jittering effects of the
upstream PLL and/or DLL units. However, this would possibly
excessively restrict the maximum frequency at which the circuit
configuration containing the various components IC1, IC2, IC3
functions. Moreover, separately supplying the external reference
clock pattern to each individual component via a separate clock
line, such as CLK1, CLK2, CLK3, would compel a certain clock tree
structure, which connects the individual components and in
particular ICs to one another, and thus in practice might overly
severely impair the freedom of choice in terms of the course of
conductor tracks. Furthermore, furnishing the external reference
clock signal EXT parallel in this way over separate supply lines
would be all the more difficult, the higher the number of
components there are that must be synchronized. This is because
then the differences in the transit path because of different
lengths of the supplying clock lines to the individual components
would become greater and greater.
In summary, accordingly, a main IC, such as IC2, exchanges data
signals with a further component, in particular an IC, such as IC3,
bi-directionally and should additionally receive data,
synchronously with its internal clock signal, from a further
component, in particular an IC, such as IC1. The main IC IC2 is
operated synchronously with a main clock, that is, an internal
reference clock signal COU21. This signal is received via an
external clock line CLK2, is carried internally in the component
IC2 via a DLL unit, and generates the internal reference clock
COU21, which assures that message signals are processed, output
and/or received exactly synchronously with the external reference
clock signal EXT. If the main IC IC2 is now also supposed to
receive data synchronously with the internal reference clock or to
the internal reference clock COU12 from the further component IC1,
then the first component IC1 could transmit the data synchronously
to an externally supplied main clock EXT. The component IC1 would
then receive the externally supplied main clock EXT and would
generate a transmission clock via a DLL unit and then send the data
signals to be transmitted to the second component IC2 synchronously
with the transmission clock. However, by the connection of PLL and
DLL units in line with one another, differences could occur between
the transmission and reception clocks, for instance from jittering
effects, different phase relationships, and so forth.
These problems can now be avoided in a simple way by providing that
the component IC2 that receives the message signals SI transmits
its internal reference clock signal over its own data line RTL to
the component IC1 that is sending the signals SI. From the
reference clock signal RT returned to the transmitting component
IC1, the transmission clock COU12 for the output unit, in
particular the driver unit AT1, of the transmitting component IC1
for the signals SI to be transmitted is generated, in such a way
that the signals SI transmitted over the signal line TL12 arrive
synchronously with the internal clock signal COU21 of the receiving
component IC2 in its receiver unit T21 and are read out
synchronously by the latter. That is, if the reception clock of the
receiving component IC2 is transmitted to the transmitter component
IC1, then the transmitter component IC1 can synchronize to that
clock, that is, to the reference clock with which the receiving
component IC2 receives the data or message signals to be
transmitted. Thus any interference or errors and in particular
phase offsets, which can occur because of the connection of various
PLL and/or DLL units in line with one another, are largely
avoided.
If only the external reference clock were supplied to each
component, then a time lag or delay of +100 psec could be slipped
into the component IC2 compared to the clock pattern of the
external reference clock EXT, for instance, while via the external
clock line CLK1, compared to the external reference clock EXT, a
time lag of -100 psec would be caused by the delay member DLL1. The
overall result between the internal clock signals or clocks of the
first component IC1 and second component IC2, a time offset of 200
psec, which is twice as long as the total chronological error or
relative offset, would result, so that any synchronization of the
two components IC1, IC2 to one another would largely be lost. In
comparison, by the feedback of the internal clock signal of the
receiving component IC2 to the transmitter component IC1 and its
use there as a reference clock, it is avoided from the very outset
that any time lag, such as 100 psec in this case, could be slipped
in by the delay member DLL2 of the component IC2 and have an effect
on the relative chronological position of the internal clock
signals of the two components IC1, IC2 to one another. Thus in this
example, only an offset or error of 100 psec between the two
internal clock signals of the components IC1, IC2 could result
because of the delay member DLL1.
The logic/memory component IC1 to which the internal clock signal
COU21 of the receiving component IC2 is supplied as a reference
clock RT can in particular be formed by an external device, such as
an oscillator scope), function generator, bit error rate tester, or
other testing device. This device can, by forwarding the internal
clock signal of the receiving component, furnish message signals,
such as data, commands, addresses, and so forth, largely
synchronously, or in other words at the instants of reception,
which are fixed in a defined way, of the receiving component, to
the input thereof, which makes the testing of such complicated
components as in this case a chip set 1C2 and its cooperation with
other components, as in this case an SDRAM memory 1C3, easier.
By outputting the internal clock signal of the receiving component,
which actually trips the reception of the signals to be
transmitted, and whose further use as a transmission clock for the
data output of a second component, substantially higher precision
is attained, with which data can be transmitted between two
components, while at the same time the complication and expense are
reduced compared to existing data transmission methods, such as
those using an additional indicator signal. Thus higher data rates
in communication among a plurality of components can be achieved.
Instead of an external reference signal that is brought to each
individual component via a single PLL member, the receiving
component now makes its reception clock available, which is used by
the transmitter component as its basic clock. The data, or signals,
to be transmitted are thus sent synchronously to the reference
clock of the receiving component. At the same time, a complicated,
expensive tree structure of externally supplied clock lines is
avoided.
In the transmitting logic/memory component IC1, the reference clock
RT of the receiving component IC2, which is arriving over the clock
signal line RTL. is expediently delayed in such a way, with the aid
of at least one delay unit, in particular a DLL member DLL1, that
the periodic clock pattern of the transmission clock COU12 at the
output of the DLL member DLL1 in the component IC1 lags one cycle
time behind, reduced by twice the signal transit time for the
transit paths along the two data lines RTL, TL12, compared to the
clock pattern of the reference rate in the receiving component IC2.
The reference clock RT carried to the transmitting component IC1 is
thus modified in the transmitter component IC1 such that the signal
SI to be transmitted at defined reception times of the internal
reference clock COU21 of the receiving component IC2 arrive in the
receiver unit T21 thereof. The receptions times can be formed for
instance by the leading edges of the periodic square high/low clock
pattern of the internal reference clock.
FIG. 2, using clock patterns in the receiving component IC2 and the
transmitting component IC1, shows how the transmission clock can be
fittingly generated in the transmitting component IC1 from the
transmitted reference clock RT on the reception side, in such a way
that the signals SI to be transmitted arrive as exactly as possible
at the specified, defined receiving times in the receiving
component IC2. In the upper half of the drawing, a time t is
plotted along the abscissa. Along the ordinate, a periodic high/low
clock pattern of square voltage pulses is shown, which succeed one
another at equidistant time intervals. The higher levels H define a
first state, such as a Boolean logical 1, while the lower level
states L define a second state, such as a logical 0. The clock
pattern thus formed can be used for instance for the internal
reference clock COU21 in the receiving component IC2. A cycle time
CT of the periodic clock pattern is preferably determined by two
successive leading edges of two adjacent square pulses H. If the
internal clock pattern of the receiving component IC2 is now
transmitted as a reference clock RT to the transmitting component
IC1 over a clock line RTL, then a transit time delay DEL can occur
because of the line length of RTL, capacitive and/or inductive
overcouplings, capacitive load switching of the clock transmitter,
and other interference factors. In the transmitting component IC1,
the reference clock CIN21 thus arrives with a time lag DEL compared
to the originally sent reference clock RT that is present at the
output of the receiving component IC2. A starting time t1* of each
square pulse is accordingly shifted, in the reference clock signal
CIN21 received by the transmitter IC1, by the delay time DEL
compared to a starting time t1 of the reference clock COU21
originally furnished by the receiving component IC2. Since the
signal line TL12 is essentially equivalent, in the opposite
direction for the signals SI to be transmitted, to the clock line
RTL in terms of its transit path, its wiring, and other properties,
a corresponding time lag DEL is brought about upon a signal
transmission over the signal line TL12. Taking the transit time
delay DEL into account, in the transmitting component IC1 with the
aid of the DLL member DLL1 or some other logic circuit or other
function, the transmission clock COU12 is generated in such a way
that compared to the reference clock COU21 originally furnished by
the receiving component IC2, it is earlier by the amount of the
delay time DEL; that is, the starting time t1** of the transmission
clock COU12 in the transmitting component IC1 is chronologically
earlier than the starting time t1 of each square pulse of the
originally furnished reference clock COU21 on the reception side.
The reference clock CIN21 arriving at the transmitting component
IC1 is to that end delayed in the transmitting component IC1 such
that the transmission clock COU12 for the output driver AT1 for
each clock cycle follows later by one cycle time, minus twice the
transit time delay 2DEL. The starting time t1** of the first square
pulse of the transmission clock COU12 is accordingly shifted
chronologically by the cycle time CT, minus twice the transit time
difference 2DEL, that is, VZ=CT-2DEL, compared to the starting time
t1* of the first square pulse H of the reference clock pattern
CIN21. The transmission clock pattern COU12 is thus shifted
earlier, compared to the reception clock pattern COU21, by a single
transit time lag DEL for the signal transit time over the signal
line TL12. The transmission clock COU12 then defines the clocking
or triggering for the outputting of the signals SI to be
transmitted. If for instance the leading edge of each square pulse
of the transmission clock COU12 is used as the transmission time
for signals SI to be sent, then the signals largely arrive exactly
at the defined reception times, namely at the instant of a leading
edge of the original reference clock COU21 in the receiving
component IC2. Synchronous data processing between the two
components IC1, IC2 is thus assured in both a simpler and a
more-reliable manner.
In summary, in the exemplary embodiment of FIG. 1, the common
external clock signal EXT for the two components IC2, IC3
communicating bi-directionally with one another is used, which at
DDR (double data rate) is a conventional method. Addresses and
commands are synchronized to the clock signal. In the data
transmission, a DQS signal is used as the reference signal or
indicator signal. The reference signals for the bi-directional data
transmission between the two components IC2, IC3 always travel in
the same direction as the data signals to be transmitted. If data
are now to be received from a further, third component by the
component IC2 synchronously with its internal main clock signal,
then to that end the internal reference clock is transmitted to the
further transmitting component IC1. From the reference clock RT
received from the receiving component IC2, the transmitting
component IC1 generates a transmission clock fittingly, such that
the data to be transmitted arrive in the receiving component
synchronously with the reception times of the internal reference
clock of that component. A synchronous system can thus be
constructed, which receives data at a fixedly defined, single rate.
This makes data transmission by the pipeline method among a
plurality of components or component groups possible. For instance,
data from a first memory component, such as the IC1, can be read
out, delivered at the same rate to a second logic component, and
further processed in this latter component. At the same time, at
the same clock rhythm, additional data can be sent from the logic
component IC2 to at least the third component IC3 or received by
that component. The second component thus outputs data, further
processed at the same internal clock rhythm, to at least one third
component or receives additional data from that component. In this
way, any errors or interference in terms of the clocking in the
various components resulting from different DLL and PLL parameters
are largely avoided.
Expediently, the various component groups or components
communicating with one another can be combined with some or all of
them on a single printed circuit board or in a single IC.
* * * * *